Composite eutectic alloy and article

ABSTRACT

A unidirectionally solidified anisotropic metallic composite body of improved stability and high temperature properties is provided with a solid solution matrix of a superalloy of the nickel-base or cobalt-base type and comprising, by weight, at least about 2% Re and less than about 0.8% Ti. Embedded in the matrix is an aligned carbide reinforcing fibrous phase, preferably one selected from carbides of Ta, V or their alloys and mixtures.

United States Patent [1 1 Smashey Sept. 9, 1975 COMPOSITE EUTECTIC ALLOY AND ARTICLE [75] Inventor: Russell W. Smashey, Loveland,

Ohio

[73] Assignee. General Electric Company,

Cincinnati, Ohio [22] Filed: June 1, 1973 [21] Appl. No.: 366,047

[52] US. Cl. 75/170; 75/171; 148/32;

148/325 [51] Int. Cl. C22c 19/00 [58] Field of Search 75/171, 170; 148/32, 32.5

[56] References Cited UNITED STATES PATENTS 3,276,865 10/1966 Freche et a1. 75/171 1/1968 Wheaton 75/l71 9/1970 Quigg et al. 75/171 Primary ExaminerR. Dean Atmrney, Agent, or FirmLee H. Sachs; Derek P. Lawrence 5 7 I ABSTRACT A unidirectionally solidified anisotropic metallic composite body of improved stability and high temperature properties is provided with a solid solution matrix of a superalloy of the nickel-base or cobalt-base type and comprising, by weight, at least about 2% Re and less than about 0.8% Ti. Embedded in the matrix is an aligned carbide reinforcing fibrous phase, preferably one selected from carbides of Ta, V or their alloys and mixtures.

14 Claims, 3 Drawing Figures J71!!! "/ldd/Ja PATENTED 35F 91975 sum 2 [1f 2 COMPOSITE EUTECTIC ALLOY AND ARTICLE The invention herein described was made in the course of or under a contract, or a subcontract thereunder, with the United States Department of the Air Force.

BACKGROUND OF THE INVENTION The present invention relates to eutectic superalloy articles and compositions and, more particularly, to such articles and compositions which include a superalloy matrix reinforced with embedded aligned carbide fibers.

The performance requirements for gas turbine engines such as those which power aircraft are constantly increasing with advanced designs. Hence, there is a continuing need for improved materials such as for turbine components which operate under strenuous high temperature environmental conditions. Materials used in such components can be critical in affecting over-all engine performance and can allow a designer to increase either power generated, operating temperatures, component life or combinations of these.

Development of the superalloys based on nickel or on cobalt, and widely used for many years in the gas turbine engine art, has now reached a point at which advances are based not only on the superalloy itself but also on orientation of the phases of the superalloy or inclusion of reinforcing members, such as fibers, which can be formed in situ during solidification of the alloy. One form of such solidification which has been used and has been widely reported is generally referred to as unidirectional solidification.

lt was recognized that such unidirectional solidification of eutectic alloys was a feasible method for producing metallic composites including aligned fibers as a reinforcement in a matrix. Such eutectic composites offered the possibility of achieving high strength in at least one of the aligned eutectic phases and also offered the possibility of achieving a strong bond between phases. Previously reported as composites consisting of a nickel-base superalloy including a TaC carbide reinforced eutectic aligned within the nickel-base matrix as a result of unidirectional solidification. A problem which can exist with such a structure involves degradation of the aligned carbide fibers resulting in loss of high temperature strength. Such degradation can occur from formation at the fiber matrix interface of undesirable structures, for example related to gamma prime and to the effect of various elements on the formation of the fibers themselves or on adjacent phases or structures. Thus the stability and high temperature properties of the alloy and the article made therefrom were affected.

SUMMARY OF THE INVENTION It is a principal object of the present invention to provide an improved composite eutectic alloy having a superalloy matrix strengthened with an aligned carbide reinforcing fibrous phase which has improved resistance to degradation which can occur from interaction between the fibrous phase and the matrix.

Another object is to provide such an alloy which can be used in unidirectional solidification to provide an improved article.

A more specific object is to provide an improved composite eutectic alloy and article having a predomi- 2 nantly TaC reinforcing fibrous phase embedded in an improved nickel base superalloy matrix, the composition of which has been adjusted to inhibit formation of phases or compounds which tend to degrade the carbide reinforcing fibrous phase.

These and other objects and advantages of the present invention will be more fully appreciated and understood from the following detailed description, its examples and the drawings, all of which are presented as representative of rather than limiting on the present invention.

Briefly, the present invention provides an article having a unidirectionally solidified anisotropic metallic composite body which includes a solid solution matrix and an aligned carbide reinforcing fibrous phase embedded in the matrix. The matrix is of a superalloy based on Ni or C0 and includes, by weight, at least about 2% Re to strengthen the matrix along with less than 0.8% Ti to avoid generation of phases or compounds which would tend to degrade the carbide reinforcing fibrous phaseflt is preferred that such carbide reinforcing fibrous phase be predominantly TaC or VC or their combinations, particularly when the superalloy is based on Ni.

In a preferred form of the present invention having a Ni-base, the alloy composition comprises, by weight, 3 to less than 10% Cr, 2 to less than 8.6% Al, less than about 0.8% Ti, 3-15% Ta, 0.1 to about 1% C, at least about 2% Re, up to about 10% of each of Co, W and V, up to 3% Mo, less than about 3% Ch with the balance essentially nickel and incidental impurities. An example of one preferred form of the alloy within that range consists essentially of, by weight, 3-8% Cr, 4-7% Al, less than 0.8% Ti, 5-1 1% Ta, 0.4-0.8% C, 27% Re, up to about 5% Co, up to about 4% W, 2-7% V, with the balance essentially Ni and incidental impurities.

In a preferred form of the invention having a C0- base, the alloy composition comprises, by weight, up to 20% Cr, 5-20% Ni, up to 8% W, 720% Ta, 0.5-1 .3% C, 2-9% Re with the balance essentially Co and incidental impurities. An example of a preferred form within that range consists essentially of, by weight, 10-16% Cr, 715% Ni, 1-6% W, 10-15% Ta, 0.5-1% C, 26% Re with the balance Co and incidental impurities.

Thus, the alloy of the present invention, which is capable of developing an improved combination of stability and high temperature properties through unidirectional solidification, comprises either a Ni-base or a Co-base superalloy which includes, by weight, at least 2% Re, less than about 0.8% Ti, 0.1 to about 1.3% C and about 3-20% Ta.

BRIEF DESCRITPION OF THE DRAWlNGS FIG. 1 is a graphical comparison of stress rupture data of the present invention with another TaC fiber strengthened alloy structure and with a very strong ordinary superalloy;

FIG. 2 is a graphical comparison of ultimate tensile strength data of the present invention with another TaC fiber strengthened alloy structure and with a very strong ordinary superalloy; and

FlG. 3 is a graphical Comparison of 0.2% yield strength data of the present invention with another TaC fiber strengthened alloy structure and with a very strong ordinary superalloy.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although thee combination of a nickel-base or cobalt-base superalloy in which is embedded aligned carbide fibers have great potential for improved proper ties, a careful compositional balance must be attained between the matrix and the fiber in order to strengthen the matrix while avoiding detrimental interaction between the matrix and the fiber. If such an alloy system is to be made into an article for use in the turbine section of advanced jet engines, it must have stability'and good high temperature properties, particularly stress rupture properties which are one of the limits to airfoil metal temperature and stress.

During the evaluation of some nickel-base eutectic alloys strengthened by TaC fibers, it was observed that a large drop in high temperature strength seemed to occur as a result of gamma prime film formation about the TaC fibers. Also, it appeared that the precipitation of chromium-rich M C needles at the TaC fiber/matrix interface not only degraded the fiber but also acted as stress risers, thereby contributing to reduced high temperature rupture strength.

During an analysis in the development of the present invention on such nickel-base carbide reinforced eutectic superalloy, it was recognized that the inclusion of the element Re had a significant effect in strengthening the matrix, particularly to dramatically increase high temperature stress rupture life. In addition, it was also seen that the presence of even relatively small amounts of titanium, for example as low as about 1 weight percent, while desirable for effective gamma prime precipitation formation, severely reduced the amount of TaC fibers which could form. The presence of Ti resulted in less desirable fiber morphology, apparently as a result of a strong thermodynamic driving force to form TiC as compared with the formation of TaC and the apparent tendency for the Ti-rich monocarbide to have a dendritic rather than rod morphology.

Thus an important characteristic of the present invention is that the superalloy matrix, in which the aligned carbide reinforcing fibrous phase is formed and embedded, includes less than about 0.8% Ti and at least about 2% Re in the presence, in the Nibase form, of relatively low amounts of Cr. In one Ni-base form, the alloy of the present invention consists essentially of, by weight, 3 to less than Cr, 2 to less than 8.6% A1, less than 0.8% Ti, 315% Ta, 0.1 to about 1% C, at least about 2% Re, up to about 10% of each of Co, W and V, up to 3% Mo, less than about 3% Cb with the balance essentially nickel and incidental impurities. As will be described in more detail in connection with the examples, another form of the present invention selects such composition to be, by weight, about 3-870 Cr, about 47% Al, less than about 0.8% Ti, 5-11% Ta, O.4O.8% C, 27% Re, 27% V, up to about 5% Co, up to about 4% W with the balance essentially Ni and incidental impurities. A more specifically preferred form by weight is 3-6% Cr, 47% Al, less than about 0.8% Ti, 7-1 1% Ta, O.5O.7% C, 57% Re, 2-4% Co, 24% W, 47% V with the balance essentially Ni and incidenta] impurities.

As was mentioned before, the composition of the alloy of the present invention, which can be unidirectionally solidified to form the present inventions article of manufacture, includes a careful balance of elements to strengthen the matrix and to provide the capability of producing a higher volume fraction of carbide fibers. One of the important matrix strengtheners included in the alloy of the present invention is Re which also has a tendency to force hardeners such as Ta and V into gamma prime in the Ni-base form. This increases the stress rupture properties dramatically, as will be shown in more detail later. Unlike the element W, Re is not a carbide former. Similarly, it has been found through evaluation that such elements as Os, Ru, Hf, Mo and W, some of which are included in the alloy of the present invention, are not equivalent to Re in that they do not have the same effect. It has been found that the inclusion of less than about 2 weight percent Re does not improve stress rupture strength appreciably. Therefore the present invention includes the element Re in the amount of at least about 2 weight percent. From a practical viewpoint, based on the high cost of Re and the decreasing benefit in greater amounts, it is less practical to include greater than about 9% Re.

As has been discussed, Ti interfers with the formation of the carbide fibers. It has been found that as low as 0.8 weight percent Ti disrupts carbide fiber formation. Therefore the alloy of the present invention specifies that at most only a trace of Ti should be present and in any event less than 0.8 weight percent.

Although the inclusion of the element Cr is beneficial from the standpoint of improving oxidation resistance, in the Ni-base form of the present invention it is maintained relatively low because of an instability it can introduce in the carbide fiber. At 10% or greater Cr, the Ni-base product is metallurgically unstable and causes the precipitation of M C reflecting the degeneration of the MC fiber, principally TaC fiber. At about 8% Cr, approaching the upper limit of allowable Cr in the Nibase form of the present invention, the strength is only somewhat better than that of an ordinary, good superalloy. However, lower within the range of 38 weight percent Cr, and more specifically within the range of about 36 weight percent, the properties are significantly improved, as will be shown by the following examples. It has been recognized, however, that less than about 3 weight percent Cr in the Ni-base form is insufficient to provide meaningful benefit either from an oxidation resistance or a strength viewpoint.

The principal carbide fiber former in the present invention is the element Ta. In the Ni-base form, it can be included within the range of about 3-15 weight percent and preferably in the range of 510% along with a balance of other elements so as not to deplete the gamma prime content in the alloy. In addition to its acting as a carbide fiber former, the element Ta also is a gamma prime former in the Ni-base form. Amounts of Ta less than about 3 weight percent in the Ni-base form and about 7% in the Co-base form are insufficient to react with carbon in the formation of TaC. In the Ni-base form, greater than about 15 weight percent Ta, in combination with Al, V and W levels included within the scope of this invention, exceeds matrix solubility resulting in undesirable phases or carbide morphologies.

The element Cb, which is sometimes associated with Ta, is not a full substitute for Ta and tends to weaken the alloy structure when included. Even as little as 1.6 weight percent Cb has been seen to have a weakening effect when substituted directly for an equivalent amount of Ta. The present invention specifies that less than 3 weight percent Cb be included in the alloy and article of the present invention provided the balance of the composition is adjusted to accommodate Cb.

An element which can react along with Ta to form a carbide fiber is V. In addition, it also reacts with Ni in the Nibase form to form gamma prime and thus can replace Ti which is substantially removed from the composition of the alloy of the present invention. Thus, V is specifically preferred to be included in the Ni-base form of the present invention and in the range of about 4-7 weight percent. Below about 4 weight percent V the alloy tends to become somewhat weaker though still an imprc't ed composition, for example at 2.3 weight percent as will be shown in the subsequent examples. In excess of about 7 weight percent, oxidation resistance tends to decrease progressively so that at about weight percent V oxidation resistance is reduced to an undesirable level. Thus, although V can be detrimental to oxidation resistance, it can be included in the Ni-base alloy of the present invention up to about 10 weight percent and preferably in the range of 4-7 weight percent to provide additional reaction with Ta and C to fonn carbide fiber as well as to provide additional gamma prime for matrix strengthening.

Another of the gamma prime formers included in the composition of the Ni-base form of the present invention is Al in the range of 2 to less than 8.6 weight percent. Amounts of 8.6% A1 or more approaches too closely to a full gamma prime matrix. Such a matrix is different from that of the present invention which is a solid solution reinforced with gamma prime and carbide fibers. As will be shown, an 8.6% A1 content places the composition past the eutectic point, introducing primary gamma prime dendrites in the matrix. Thus aluminum at about 8.6 weight percent causes serious loss of stress rupture strength. However, although A1 is needed for gamma prime strengthening in the carefully balanced composition of the present invention, it has been recognized that less than about 2 weight percent is insufficient for such purposes. In a preferred Nibase form of the present invention, the sum of the gamma prime formers Ta, V and Al should be no greater than about 25 weight percent when Ta is in the range of 3-15 weight percent.

Required in the composition of the present invention is the element C which is needed to combine with Ta or with Ta and V to produce the carbide fiber which strengthens the matrix. Less than 0.1 weight percent C is insufficient to form the carbide fiber. Greater than about 1 weight percent C produces free carbon because there are not enough desirable carbide formers in 6 the present composition to react with more than about 1% C. However, any such free carbon will slag off or will collect in the sorting-out portion of the casting which is adjacent the chill and which is later removed from the cast article. The amount of C included in the composition of this invention is a function of the amount of Ta, and of V, when included, sufficient to form a monocarbide of one or both of such elements.

An element which is preferred to be omitted from the composition but which can be tolerated up to about 3 weight percent is Mo. Like Cb, it tends to degrade the carbide fiber structure and reduce properties.

An element which can be included in the composition, in the range of up to about 10 weight percent, is W. It functions principally as a solid solution strengthener although it contributes somewhat to gamma prime formation. In excess of about 10 weight percent, it interfers with carbide fiber formation. Its preferred contribution occurs in the range up to about 4% and preferably in the range of about 24% in Ni-base and up to about 6% and preferably 1 6% in Co-base.

In nickel-base forms of the present invention, the element Co substitutes for nickel up to about 10 weight percent and contributes to the solubility relationship. In such smaller amounts, for example up to about 5 weight percent and preferably 2-4 weight percent, Co increases the melting point. However, at the higher amounts, for example greater than about 10 weight percent, it tends to result in matrix instabilities.

As was mentioned before, in order to provide the article of the present invention, the alloy having the above-described careful balance of elements must be unidirectionally solidified to enable the carbide eutectic fibers to form integrally within and be bonded to the reinforced solid solution matrix. Such unidirectional solidification can be conducted in one or more of the many methods and using apparatus Well-known and widely reported in the art.

During the evaluation ofthe present invention, a large number of alloy compositions were evaluated. The following Table I lists the composition of some of such alloys. A11 percentages in this Table and elsewhere in this specification are percent by weight unless otherwise stated. The alloy examples in Table I have been grouped to facilitate reference to the discussion which follows and to the comparative data of other tables or FIGURES of the drawings.

TABLE I COMPOSITIONS( WT /r Balance Ni and incidental impurities Alloy Example Cr C o W Al Tu C Re V Ti Mo C b TABLE l-continued COMPOSlTlONS(WT/r Balance Ni and incidental impurities Alloy Example Cr Co W Al Ta C Re V Ti Mo Ch Specimens of the alloys listed in Table l were melted in argon in alumina crucibles and then chill-cast into copper bar molds. Specimen castings were planar front solidified to provide the unidirectional article specimens used for subsequent testing. Mechanical test specimens for longitudinal properties were machined from the ingots parallel to the growth direction. To obtain transverse properties, test specimen blanks were electro-discharge machined normal to the growth direction. These blanks were then assembled between specimen grips and the entire assembly was ground into a mechanical test specimen configuration.

One of the essential features of the present invention is the inclusion of the element Re principally to strengthen the alloy matrix. Such strength improvement is particularly evident in the stress rupture properties of the unidirectionally solidified specimens made from the alloy composition. The following Table 11 shows the dramatic effect on stress rupture strength of the inclusion of Re within the range of the present invention on alloy compositions which otherwise are substantially the same as shown by Table l. The data presented in Table ll resulted from stress rupture testing in air.

As used in the tables, ksi means thousands of pounds per square inch, the term RA" means reduction in area, the term Elong. means elongation and P means the well-known and widely used metallurgical stress rupture relationship known as the Larson- Miller parameter P T(C Log t) X lwhere C 20, described in more detail in American Society of Engineers Transactions, 1952, Volume 74, at pages 765-771. Use of such a parameter allows a wide variety of comparisons between stress rupture lives at various temperatures and at selected stress levels.

It should be noted from the data of Table ll that even though there was a very significant improvement in high temperature stress rupture life, it was not made at a sacrifice of ductility.

During the evaluation of the present invention, alloys 1 and 4 were prepared to study the effect of Ti on the cast structure. After preparation and unidirectionally solidifying alloy 1, it was noted from photomicrographs that the structure was unsatisfactory: it included few aligned fibers and predominantly a dendrite structure. Thus it was recognized that the carbide fiber reinforcement desired in the article of the present invention could not be attained through alloy 1. Similarly, a mi crographic evaluation of alloy 4 showed that the as-cast structure was a solid solution matrix with gamma prime and equiaxed carbide particles which are known not to form the desired aligned carbide fiber structure. Thus, even as little as 0.8% Ti is detrimental to the composition of the present invention.

The specifically preferred Ni-base form of the present invention includes the optional elements Co, W and V along with the other required elements. Typical of such specifically preferred form is alloy example 13 which was selected for more extensive evaluation as represented not only by the data of Table 111 but also the comparative data shown in the drawings. As can be seen from the following Table III the stress rupture properties of alloy example 13 are better than other forms of the alloy of the present invention presented here and dramatically better than known alloys or cast articles of a type similar to that to which the present invention relates.

Comparison of the data in Table lll for alloy exam ples 13, 14 and 15 shows principally the effect of increasing amounts of Cr on the strength of the alloy. At about 8% Cr, the strength is reduced so that it begins to approach that of an ordinary, good superalloy without carbide fiber strengthening. Based on an evaluation of these and similar alloys, the present invention hasdefined the Cr range to be 3 to less than 10%, preferably 38% Cr and more specifically 3-6% Cr.

The effect of Cb is shown by examples 19 and 20 wherein even as little as 1.6% Cb in a direct, equivalent substitution for Ta, without other adjustment in the composition to accommodate Cb, results in dramatic reduction in stress rupture life. Therefore, the pre ferred form of the present invention excludes Cb from the composition.

Examples 18, 21 and 24 through 28 show the effect of varying amounts of Al and V along with variation in the level of TaC. For example, comparison of examples l8 and 28 shows that at an Al level of 8.6%, there is too much aluminum thus forcing the Ni-base alloy past the eutectic point and introducing primary gamma prime dendrites into the matrix. This has been observed from photomicrographic evaluations. This comparison, along with consideration of example 27 which shows good strength properties and is within the scope of the present invention, indicates'that the maximum allowable Al content within the scope of the Ni-base form of the present invention lies at a point between 7.4% and less than 8.6%. From these considerations, the present invention has been defined as having an Al content of less than 8.6% and preferably in the range of about 4-7%.

In a comparison of examples 26 and 27, a substitution of Al for V resulted in a slight loss in stress rupture propertiesv However, there was an improvement in oxidation resistance. Thus the alloy composition within the scope of the present invention can be selected and adjusted according to the intended application.

As was stated before and as is indicated by the data in Table III, one of the specifically preferred forms of the present invention is represented by example 13. Article specimens of this alloy form were prepared for evaluation in a variety of stress rupture and tensile tests, both in the longitudinal and transverse direction in respect to the unidirectionally solidified structure. Comparison of example 13 test data with data for the strongest TaC fiber strengthened structures and with the best reported equiaxed cast superalloy are shown in FlGS. l, 2 and 3. These figures, respectively, compare the longitudinal and transverse stress rupture strength, the longitudinal and transverse ultimate tensile strength and the longitudinal and transverse 0.2% yield strengths of the unidirectionally solidified TaC structures and those same properties for the ordinary cast superalloy. Alloy C in the drawing was in the form of a unidirectionally solidified structure the composition of which consisted nominally, by weight, of 9.5% Ni, 15.7% Cr, 3.0% W, 12.0% Ta, 0.77% C with the balance essentially Co and incidental impurities. Alloy R, sometimes referred to as Rene 120 alloy, was an ordinary superalloy with an equiaxed structure and consisted nominally, by weight, of 0.17% C, 9% Cr, 4% Ti, 0.015% B, 4.3% A1, 7% W, 2% Mo, 10% Co, 3.8% Ta, 0,08% Zr, with the balance essentially Ni and incidental impurities. Review of the data presented in the drawings shows clearly the advantage of the present invention as represented by example 13.

During the evaluation of the present invention, Cobase forms as well as Ni-base alloys were evaluated. The following Tables IV and V list the composition and stress rupture properties of two of such alloys evaluated within the broad range of up to Cr, 520% Ni, up to 8% W, 720% Ta, 0.51.3% C and 29% Re in a C0- base. As in the case of the Ni-base alloy form, the specimens were prepared by unidirectional solidification.

TABLE IV TABLE V-continued Stress Rupture Data Because Co-base alloys of the type to which the present invention relates are not gamma prime strengthened, they depend solely on solution strengthening within the matrix. In the present invention, the high strength properties are achieved from the combination of improved matrix strength through the presence of Re and reinforcement strengthening from aligned carbide fibers predominantly TaC. The composition, particularly the preferred range of 10-1 6% Cr, 715% Ni, 16% W, 10-15% Ta, 0.71% C and 26% Re in the Co-base, is selected to avoid detrimental interaction between the matrix and the aligned fibers and to assure matrix stability for example to avoid allotropic transformation.

The present invention has been described in connection with specific examples and forms. However, it will be understood by those skilled in the metallurgical art that the invention involving the inclusion of Re and the limitation of Ti in a superalloy matrix further strengthenable through aligned carbide fibers is capable of a wide variety of modifications within its scope.

What is claimed is:

1. An article of manufacture having an improved combination of stability and high temperature properties comprising a unidirectionally solidified anisotropic metallic composite body comprising:

a matrix of a Ni-base or Co-base superalloy consisting essentially of, by weight, about 2- 9% Re and less than about 0.8% Ti, along with elements selected from the group consisting of Cr, Al, Ta, C, Ni, Co, W, V, Mo, Cb, Hf, Zr and B, the matrix being a solid solution; and

an aligned eutectic reinforcing fibrous phase selected from carbides of the group consisting of Ta, V and their alloys and mixtures embedded in the matrix.

2. The article of claim 1 in which the eutectic carbide reinforcing fibrous phase is predominantly TaC.

3. The article of claim 1 in which the superalloy is Nibase consisting essentially of by weight, 3 to less than 10% Cr, 2 to less than 8.6% A1, less than about 0.8% Ti, 315% Ta, 0.1 to about 1% C, about 27% Re, up to about 10% Co, up to about 10% W, up to about 10% V, up to 3% Mo and less than about 3% Cb.

4. The article of claim 3 in which the superalloy consists essentially of, by weight, about 38% Cr, about 4-7% Al, less than about 0.8% Ti, 5-1 1% Ta, O.4O.8% C, 27% Re, up to about 5% Co, up to about 4% W, 27% V with the balance essentially Ni and incidental impurities.

5. The article of claim 4 in which the eutectic carbide reinforcing fibrous phase is predominantly TaVC.

6. The article of claim 4 in which the superalloy consists essentially of, by weight, 3-6% Cr, 47% Al, less than about 0.8% Ti, 7-11% Ta, 0.50.7% C. 57% Re, 24% Co, 2-4% W, 4-7% V with the balance essentially Ni and incidental impurities.

7. The article of claim 1 in which the superalloy is Co-base and consists essentially of, by weight, up to 1 1 20% Cr, 5-20% Ni, up to 8% W, 7-207: Ta, 0.5-1.3% C and 2-9% Re.

8. The article of claim 7 in which the superalloy consists essentially of, by weight, lO-l6% Cr, 7-1570 Ni, l6% W, -15% Ta, 0.51% C, 26% Re, with the balance Co and incidental impurities.

9. An alloy capable of developing in a unidirectionally solidified anisotropic article an improved combination of stability and high temperature properties, the alloy comprising a Ni-base or Co-base superalloy consisting essentially of, by weight, about 2-9% Re, less than about 0.8% Ti, 0.4t0 about 1.3% C and about 3-20% Ta, along with elements selected from the group consisting of Cr, Al, Ni, Co, W, V, Mo, Cb, Hf, Zr and 10. The alloy of claim 9 in which the superalloy is Nibase consisting essentially of, by weight, 3 to less than 10% Cr, 2 to less than 8.6% A1, less than about 0.8% Ti, 3-l5% Ta, 0.4 to about 1% C, about 2-7% Re, up to 12 about 10% Co, up to about 10% W, up to about 10% V, up to 3% Mo and less than about 3% Cb.

l l. The alloy of claim 10 consisting essentially of, by weight, about 38% Cr, about 47% A], less than about 0.8% Ti, 5-1 1% Ta, 0.4-0.8% C, 2-7% Re, up to about 5% Co, up to about 4% W, 27% V with the balance essentially Ni and incidental impurities.

12. The alloy of claim 11 consisting essentially of, by weight, 3-6% Cr, 47% Al, less than about 0.8% Ti, 7-] 1% Ta, 05-07% C, 57% Re, 2-4% Co, 2-4% W, 4-7% V with the balance essentially Ni and incidental impurities.

13. The alloy of claim 9 in which the superalloy is Cobase consisting essentially of, by weight, up to 20% Cr, 5-20% Ni, up to 8% W, 7-20% Ta, O.5-l.3% C and 2-9% Re.

14. The alloy of claim 13 consisting essentially of, by weight, lO-l6% Cr, 7l5% Ni, l6% W, 10-15% Ta, 0.5-l% C, 26% Re, with the balance essentially Co and incidental impurities. 

1. AN ARTICLE OF MANUFACTURE HAVING AN IMPROCED COMBINATION OF STABILITY AND HIGH TEMPERATURE PROPERTIES COMPRISING A UNIDIRECTIONALLY SOLIDIFIED ANISTROPIC METALIC COMPOSITE BODY COMPRISING: A MATRIX OF A NI-BASE OF CO-BASE SUPERALLOY CONSISTING ESSENTIALLY OF , BY WEIGHT , ABOUT 2- 9, RE AND LESS THAN ABOUT 0.8, TI, ALONG WITH ELEMENTS SELECTED FROM THE FROUP CONSISTING CR, AL, TA, C, NI, CO, W, V, MO, C''O, HF, ZR AND B, THE MATRIX BEING A SOLID SOLUTION, AND AN ALIGNED EUTECTIC REINFORCING FIBROUS PHASE SELECTED FROM CARBIDES OF THE GROUP CONSISTING OF TA, C AND THERE ALLOYS AND MIXTURES EMBEDDED IN THE MARIX.
 2. The article of claim 1 in which the eutectic carbide reinforcing fibrous phase is predominantly TaC.
 3. The article of claim 1 in which the superalloy is Ni-base consisting essentially of by weight, 3 to less than 10% Cr, 2 to less than 8.6% Al, less than about 0.8% Ti, 3-15% Ta, 0.1 to about 1% C, about 2-7% Re, up to about 10% Co, up to about 10% W, up to about 10% V, up to 3% Mo and less than about 3% Cb.
 4. The article of claim 3 in which the superalloy consists essentially of, by weight, about 3-8% Cr, about 4-7% Al, less than about 0.8% Ti, 5-11% Ta, 0.4-O.8% C, 2-7% Re, up to about 5% Co, up to about 4% W, 2-7% V with the balance essentially Ni and incidental impurities.
 5. The article of claim 4 in which the eutectic carbide reinforcing fibrous phase is predominantly TaVC.
 6. The article of claim 4 in which the superalloy consists essentially of, by weight, 3-6% Cr, 4-7% Al, less than about 0.8% Ti, 7-11% Ta, 0.5-0.7% C, 5-7% Re, 2-4% Co, 2-4% W, 4-7% V with the balance essentially Ni and incidental impurities.
 7. The article of claim 1 in which the superalloy is Co-base and consists essentially of, by weight, up to 20% Cr, 5-20% Ni, up to 8% W, 7-20% Ta, 0.5-1.3% C and 2-9% Re.
 8. The article of claim 7 in which the superalloy consists essentially of, by weight, 10-16% Cr, 7-15% Ni, 1-6% W, 10-15% Ta, 0.5-1% C, 2-6% Re, with the balance Co and incidental impurities.
 9. An alloy capable of developing in a unidirectionally solidified anisotropic article an improved combination of stability and high temperature properties, the alloy comprising a Ni-base or Co-base superalloy consisting essentially of, by weight, about 2-9% Re, less than about 0.8% Ti, 0.4to about 1.3% C and about 3-20% Ta, along with elements selected from the group consisting of Cr, Al, Ni, Co, W, V, Mo, Cb, Hf, Zr and B.
 10. The alloy of claim 9 in which the superalloy is Ni-base consisting essentially of, by weight, 3 to less than 10% Cr, 2 to less than 8.6% Al, less than about 0.8% Ti, 3-15% Ta, 0.4 to about 1% C, about 2-7% Re, up to about 10% Co, up to about 10% W, up to about 10% V, up to 3% Mo and less than about 3% Cb.
 11. The alloy of claim 10 consisting essentially of, by weight, about 3-8% Cr, about 4-7% Al, less than about 0.8% Ti, 5-11% Ta, 0.4-0.8% C, 2-7% Re, up to about 5% Co, up to about 4% W, 2-7% V with the balance essentially Ni and incidental impurities.
 12. The alloy of claim 11 consisting essentially of, by weight, 3-6% Cr, 4-7% Al, less than about 0.8% Ti, 7-11% Ta, 0.5-0.7% C, 5-7% Re, 2-4% Co, 2-4% W, 4-7% V with the balance essentially Ni and incidental impurities.
 13. The alloy of claim 9 in which the superalloy is Co-base consisting essentially of, by weight, up to 20% Cr, 5-20% Ni, up to 8% W, 7-20% Ta, 0.5-1.3% C and 2-9% Re.
 14. The alloy of claim 13 consisting essentially of, by weight, 10-16% Cr, 7-15% Ni, 1-6% W, 10-15% Ta, 0.5-1% C, 2-6% Re, with the balance essentially Co and incidental impurities. 